Separation and purification of methyl ethyl ketone



INVENTOR NAT C. ROBERTSON 4ATTO RNEVS,

, f, Y e B 235.50

Filed June 14,

` N. c. RoBERTsoN Juy 26, 1949.

SEPARATION AND PURIFICATION oF METHYL ETHYL KEToNE Patented July 26,1949

SEPARATION AND PURIFICATION OF METHYL ETHYL KETONE Nat C. Robertson,Corpus Christi, Tex., assignor to Celancse Corporation of America, acorpol'a.-v

tion of Delaware Application June 14, 1948, Serial No. 32,901 Claims.(Cl. 202--39.5)

This invention relates to the production of purified organic compoundsand relates more particularly to the separation and purification of.

certain mixtures of organic compounds obtained as a product of the vaporphase partial oxidation, with air or oxygen, of gaseous hydrocarbons,such as propane, butane, or mixtures thereof.

An object of this invention is the provision of an improved process forthe separation of purified methyl ethyl ketone and tetrahydrofuran froma crude fraction of the mixture of products obtained on the vapor phasepartial oxidation, with air or oxygen, of gaseous aliphatic hydrocarbonssuch as, propane, butane, or mixtures thereof.

Other objects of this invention will appear from the following detaileddescription and the accompanying drawing.

In the drawing, the ligure is a schematic diagram, or flow sheet, ofapparatus employed in connection with my novel process.

The vapor phase, partial oxidation of aliphatic hydrocarbons such aspropane or butane, or mixtures thereof, employing air or oxygen as theoxidizing agent, yields a complex mixture of products includingformaldehyde, acetaldehyde, methanol, propionaldehyde, allyl alcohol,acetone, methyl ethyl ketone, methylal, acrolein, tetrahydrofuran,2methyl tetrahydrofuran, Various oxides, methyl formate and otheresters, formals and acetals, as well as numerous other aliphaticcompounds in varying amounts. .In order to separate the complex mixtureof oxidation products and to purify each of the components so that thesame will be suitable for commercial use, an intricateproductpurification scheme is necessary. Many of the oxidation products presentin the mixture not only boil within a relatively narrow temperaturerange but numerous constant boiling azeotropes are also formed whichmakes an efficient and economical separation even more difficult. Duringthe puriy fication a number of crude fractions each-containing aplurality' of compounds is obtained. One such fraction comprises amixture -of tetrahydrofuran, 2-methyl tetrahydrofuran, methyl ethylketone, formals, acetals and oxides dissolved in pentane and obtainedduring an extractive distillation with pentane. The methyl ethyl ketoneis present in the mixture, from which the pentane is stripped, inappreciable amount but the recovery of the same in a highly purifiedform from the mixture remaining after the pentane is stripped olf isquite difiicult. This' is due to the fact that certain of the acetalstend to remain with the methyl ethyl ketone as contaminants since theirsolubilities and other physical characteristics are very similar.

I have now found that the methyl ethyl ketone may be separated from theaforementioned mixture, in which it is present together withtetrahydrofuran, 2-methyl-tetrahydrofuran and the several formals,acetals and oxides mentioned, in

an eiiicient and economical manner and in a highly puriiied form. Inaccordance with my novel process, the desired separation may be effectedif the fraction of said mixture boiling between about 68 and 75 C. ismixed with, say, 1 to 4 volumes of hexane and azeotropically distilled,the distillate comprising essentially a mixture of methyl ethyl ketoneand hexane containing some acetals, and then separating the methyl and`ethyl ketone from the distillate. This separation is eiected by washingthe distillate with water whereby the water-soluble methyl ethyl ketoneis extracted together with at most about 5%, based on the weight of themethyl ethyl ketone, of acetals and then subjecting the aqueous extractto a water-extractive distillation which serves to remove the acetals.The distillate from the water extractive distillation comprises anazeotrope of methyl ethyl ketone and water. The methyl ethyl ketonepresent in the condensed azeotropic distillate is removed by extractingthe latter with a water-immiscible solvent for the methyl ethyl ketone,such as pentane. On distillation of the pentane extract, the

' pentane comes over as the distillate and is remethyl ethyl ketone,tetrahydrofuran, Z-.methyl tetrahydrofuran, formals, acetals and oxides,is fed to a light ends column l provided with a condenser '2 and areceiver 3 and the fraction boiling below about 68 C. taken off. A sidestream is continuously removed from the reboiler 4 of column I andpassed to a heavy ends col-V umn 5 provided with a condenser 6 and areceiver l. The fraction coming over' up to about 75 C. is taken off incolumn 5, mixed with 1 to 4 volumes of hexane and the mixture fed to ahexane column 8. Column 8 is provided with la condenser 9 and a receiverI0. The fraction coming over up to about C., and consisting of a mixtureof hexane and methyl ethyl ketone, is taken off in column 8 and theresidue in reboiler Il is discarded. A side stream of the distillatefrom receiver Ill-is taken oif as shown, mixed with 4 to 8 volumes ofwater for each volume of the side stream and the mixture fed to a waterextractor I2.

The water acts to extract the methyl ethyl ketone from the hexanepresent and also removes the small amount of acetals from the solution.Since the water and hexane are immiscible two layers are formed in waterextractor I2, the upper layer being hexane and the lower layercomprising, an aqueous solution of methyl ethyl ketone. The hexane layeris recycled and the water extract continuously fed to a water-extractivedistillation column I3 provided with acondenser I4 and a -recever I5.Water is also fed to the column in yl ketone-water azeotrope taken olfcolumn I3 is then mixed withfrom 2 to 4 volumes of pentane andintroduced into an extractor Il. The upper pentane layer which forms inthe extractor contains the methyl ethyl ketone and is continuouslyremoved and fed to a pentane recovery column IB provided with acondenser I9 and a receiver 20. The pentane present comes off overheadand recycled to pentane extractor Il, while the purified methyl ethylketone is removed from reboiler 2l at the base of column I8,

It is to be understood that the foregoing detailed description may begiven merely by way of illustration and that many variations may be madetherein without departing from the spirit of my invention.

Having described my invention, what r desire to secure by Letters Patentis:

1.- Process for the separationand purlcation of methyl ethyl ketone froma mixture comprising methyl ethyl ketone, tetrahydrofuran, 2-

methyl tetrahydrofuran, formals, acetals andl u oxides.' which comprisesfractionating the mixture to separate therefrom a fraction boiling fromabout 68 to 75 C., mixing said fraction with hexane, distilling themixture and separating a mixture of hexane and methyl ethyl, ketonefromand to distill off an azeotrope consisting of methyl ethyl ketone andwater, extracting the azeotrope with pentane whereby the methyl ethylketone is removed and stripping the pentane from the methyl ethyl ketoneto yield puried methyl ethyl ketone.

2. Process for the separation and purification ofmethyl ethyl ketonefrom a mixture comprising methyl ethyl ketone, tetrahydrofuran, 2-

methyl tetrahydrofuran, formals, acetals and.

ketonel boiling up'to about 65 C., washing they distillate with watertoextract the methyl ethyl ketone, subjecting the aqueous extract to awater extractive distillation by introducing alarge volume of 'water inthe vapors so that the equilibrium.czori'centiation of water where thewater is introducedis about 50-80 volume per cent to wash theacetalstherefrom and` to distill of! anazeotrope consisting of methylethyl ketone and 'waten extracting the azeotrope with pentane wherebythe methyl ethyl ketone is removed and 76' 2,381,032 Bludworth Aug. 7,1945 4 stripping the pentane from the methyl ethyl ketone to yieldpurified methyl ethyl ketone.

3. Process for the separation and purification of methyl ethyl ketonefrom a. mixture comprising methyl ethyl ketone, tetrahydrofuran, 2-methyl tetrahydrofuran, formals, acetals and oxides, which comprisesfractionating the mixture to separate therefrom a fraction boiling fromabout 68 to 75 C., mixing said fraction with from about 1 to 4 volumesof hexane, distilling the mixture and separating therefrom a. mixture ofhexane and methyl ethyl ketone boiling up to about 65 C., washing thedistillate with water to extract the methyl ethyl ketone, subjecting theaqueous extract to a water extractive distillation to wash the acetalstherefrom and to distlll of! an azeotrope consisting of methyl ethylketone and water, extracting the azeotrcpe with pentane whereby themethyl ethyl ketone is removed and stripping the pentane from the methylethyl ketone to yield purified methyl ethyl ketone.

4. Process for the separation and purication of methyl ethyl ketone froma mixture comprising methyl ethyl ketone, tetrahydrofuran, 2- methyltetrahydrofuran, formals, acetals and oxides, which comprisesfractionating the mixture to separate therefrom a fraction boiling fromabout 68 to 75 C., mixing said fraction with from about 1 to 4 volumesof hexane, distilling the mixture and separating therefrom a mixture ofhexane and methyl ethyl ketone boiling up to about 65 C., washing thedistillate with water to extract the methyl ethyl ketone, subjecting theaqueous extract to a water extractive distillation by introducing alarge volume of water into the vapors so that the equilibriumconcentration of water where kthe water is introduced is about 80 volumeper cent to wash the acetals therefrom and to distill oii an azeotropeconsisting of methyl ethyl ketone and water, extracting the azeotropewith pentane whereby the methyl ethyl ketone is removed and strippingthe pentane from the methyl ethyl ketone to yield purified methyl ethylketone.

5. Process for the separation and purification of methyl ethyl ketonefrom a mixture comprising methyl Vethyl ketone, tetrahydrofuran, 2-methyl tetrahydrofuran, formals, acetals and oxides, which comprisesfractionating the mixture to separate therefrom a fraction boiling fromabout 68 to 75 C., mixing said fraction with from about l to 4volumes-of hexane, distilling the mixture and separatingtherefrom amixture of hexane and methyl ethyl ketone boiling up to about 65 C.,washing the distillate with water to extract the methyl ethyl ketone,subjecting the aqueous extract to a water extractive distillation byintroducing a large volume of water Y into the vapors so that theequilibrium concentration of water where the water is introduced isabout 80 volume per cent to wash the acetals therefrom and to distilloilA an azeotrope consisting of. methyl ethyl ketone and water,extractville of this patent:

ing the azeotrope withfrom 2 to 4 volumes of pentane whereby the methylethyl ketone is removed and stripping the pentane from the methyl ethylketone to yield purified methyl ethyl ketone.

. NAT C. ROBERTSON.

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